Heat Stress Induced by the Navy Fire Fighter's Ensemble Worn in Various Configurations

The Navy Clothing and Textile Research Facility conducted a laboratory evaluation to compare heat stress when the Navy Fire Fighters Ensemble NFFE is worn in three configurations 1 coverall buttoned up with anti-flash hood, helmet and gloves worn, 2 coverall unzipped with hood around neck and no helmet or gloves worn, and 3 coverall down around the waist with hood around neck and no helmet or gloves worn. The effectiveness of a selected cooling vest in reducing this heat stress wa also examined. Nine test volunteers underwent six, 2-hour heat exposures three NFFE configurations with and without the cooling vest. Environmental conditions were 90 deg F dry bulb temperature with 60 relative humidity. During the heat exposures, the test volunteers alternated seated rest with walking at 3.5 mph on a treadmill every 15 minutes. These conditions were chosen to simulate a training drill during which the level of physical exercise is low. Thermal strain, as measured by rectal temperature, skin temperatures, heart rate and sweating rate, was greatest when the NFFE was buttoned up. Unzipping the coverall resulted in a moderate decrease in thermal strain. When the coverall was worn down around the waist, all indicators of thermal strain were significantly reduced. Use of the cooling vest in both the buttoned up and unzipped configurations significantly reduced thermal strain. When the coverall was worn down around the waist, and the level of thermal strain was only moderate, the vest only slightly reduced heat stress.